Effects of physical activity and feed and water restriction at reimplanting time on feed intake patterns, growth performance, and carcass characteristics of finishing beef steers

In the feedlot, there can be a decrease in dry matter intake (DMI) associated with reimplanting cattle that negatively affects growth performance. This study was conducted to determine the mechanisms causing a decrease in DMI after reimplanting and identify a strategy to mitigate the decrease. Crossbred steers [n = 200; 10 pens/treatment; initial bodyweight (BW) = 386 ± 4.9 kg] were used in a randomized complete block design experiment. Cattle were implanted with Revalor-IS on day 0. Treatments included a Revalor-200 implant on day 90 before feeding with the following management practices imposed: 1) steers were returned to their home pen immediately after reimplant (PCON); 2) steers were placed in pens and restricted from feed and water for 4 hours (RES); 3) steers were walked an additional 805 m after reimplant and then returned home (LOC); 4) steers were restricted from feed and water for 4 hours and walked an additional 805 m (RES+LOC); 5) steers were given an oral bolus of Megasphaera elsdenii (Lactipro; MS Biotec, Wamego, KS) and were restricted from feed and water for 4 hours, then walked an additional 805 m (LACT). One-hundred steers were given an ear tag to record minutes of activity (ESense Flex Tags, Allflex Livestock Intelligence, Madison, WI). As a percentage of BW, DMI was 5% greater (P = 0.01) from reimplant to end for PCON vs. RES, LOC, and RES+LOC treatments. Likewise, as a percentage of BW, DMI was 6.6% greater (P = 0.03) from reimplant to end and 4.0% greater (P = 0.05) overall for the PCON treatment vs. the LOC treatment. Overall, DMI as a percentage of BW, was 3.3% greater (P = 0.02) for PCON vs. RES, LOC, and RES+LOC treatments. There was an increase in G:F from reimplant to end (P = 0.05) for RES+LOC vs. the LACT treatment. From these data, we conclude that restricting cattle from feed and water for 4 hours after reimplanting did not alter subsequent DMI. Increasing locomotion had the greatest negative effect on DMI and growth performance. Management strategies to decrease locomotion associated with reimplanting would be beneficial to DMI and overall growth performance of finishing beef steers.

Effect of incremental proportions of Desmanthus spp. in isonitrogenous forage diets on growth performance, rumen fermentation and plasma metabolites of pen-fed growing Brahman, Charbray and Droughtmaster crossbred beef steers

Desmanthus (Desmanthus spp.), a tropically adapted pasture legume, is highly productive and has the potential to reduce methane emissions in beef cattle. However, liveweight gain response to desmanthus supplementation has been inconclusive in ruminants. This study aimed to evaluate weight gain, rumen fermentation and plasma metabolites of Australian tropical beef cattle in response to supplementation with incremental levels of desmanthus forage legume in isonitrogenous diets. Forty-eight Brahman, Charbray and Droughtmaster crossbred beef steers were pen-housed and fed a basal diet of Rhodes grass (Chloris gayana) hay supplemented with 0, 15, 30 or 45% freshly chopped desmanthus forage on dry matter basis, for 140 days. Varying levels of lucerne (Medicago sativa) hay were added in the 0, 15 and 30% diets to ensure that all diets were isonitrogenous with the 45% desmanthus diet. Data were analyzed using the Mixed Model procedures of SAS software. Results showed that the proportion of desmanthus in the diet had no significant effect on steer liveweight, rumen volatile fatty acids molar proportions and plasma metabolites (P ≥ 0.067). Total bilirubin ranged between 3.0 and 3.6 μmol/L for all the diet treatments (P = 0.67). All plasma metabolites measured were within the expected normal range reported for beef cattle. Rumen ammonia nitrogen content was above the 10 mg/dl threshold required to maintain effective rumen microbial activity and maximize voluntary feed intake in cattle fed low-quality tropical forages. The average daily weight gains averaged 0.5 to 0.6 kg/day (P = 0.13) and were within the range required to meet the target slaughter weight for prime beef markets within 2.5 years of age. These results indicate that desmanthus alone or mixed with other high-quality legume forages can be used to supplement grass-based diets to improve tropical beef cattle production in northern Australia with no adverse effect on cattle health.

Dried distiller´s grains plus solubles supplementation improves low-quality tropical grass utilization on beef steers

ABSTRACT: This study was designed to evaluate the effect of corn dried distiller´s grains (DDGS) supplementation on feed intake, total tract digestibility, and ruminal fermentation of beef steers fed low-quality Guinea grass (Megathyrsus maximus, cv. Gatton panic). Twelve Braford crossbred steers were housed in individual pens (n = 4 steers/treatment), provided with three levels of DDGS supplement: 0%, 0.6%, or 1.2% BW. Steers were blocked by live weight and randomly assigned to treatments within the block. Corn DDGS supplementation increased total OM intake (21.55, 40.23, and 56.69 g/kg BW0.75) and tract OM digestibility (46.33, 49.03, and 72.39 % DM). Total tract digestible OM, CP, NDF and EE intake also increase in response to DDGS supplementation. Forage OM intake decreased when supplementation level reached 1.2 % BW. Also, ruminal pH decreased with DDGS supplementation level (6.88, 6.47, and 6.27). No differences were observed in total volatile fatty acids (VFA) concentration; however, the molar proportion of acetate decreased (77.98, 73.90, and 67.29 % Total VFA) as well as acetate: propionate ratio (4.38, 3.48, and 2.74). On the contrary, propionate proportions increased (18.32, 21.86, and 24.81 % Total VFA). Levels of ammonia and lactate were within suggested values for optimal fermentation and bacterial growth. Low-quality grass supplementation with corn DDGS increased total OM intake and digestibility. Also, DDGS inclusion favorably altered volatile fatty acids profile by reducing the acetate to propionate ratio regarding forage-only diets.

Impacts of polyclonal antibody preparations from avian origin as a feed additive to beef cattle: Immune responses during the step-up transition diets

This study investigated the effects of feeding an avian-derived polyclonal antibody preparation (PAP; CAMAS, Inc.) against Streptococcus bovis, Fusobacterium necrophorum, and lipopolysaccharides (40, 35, and 25% of the preparation, respectively) on immune responses [haptoglobin (Hp), serum amyloid A (SAA), rectal temperature (RT), leukocyte counts, and expression of cell adhesion molecules cluster of differentiation (CD) CD11b, CD14, and CD62L] of beef steers during a 21-d step-up adaptation to a high-grain diet. Eight ruminally cannulated Angus crossbred beef steers (658 ± 79 kg of BW) were assigned in a cross-over design and transitioned from a diet containing bermudagrass hay [Cynodon dactylon (L.) Pers.] ad libitum plus 0.45 kg/d of molasses with 0 (CON) or 3 g of PAP (PAP) to a high-grain diet. Transition consisted of three 7-d steps of increased inclusion of cracked corn (35, 60, and 82% of the diet dry matter for STEP1, STEP2, and STEP3, respectively). On each transition day and 7 d after STEP3 (STEP3-7d), RT was obtained every 3 h for a total of 24 h, whereas blood was collected on d 0, 1, and 3, relative to diet transition. There were no effects of PAP inclusion in any of the blood parameters (P > 0.11). However, a tendency for day effect (P = 0.10) was observed for concentrations of Hp, which were greater on d 3 and 7 vs. d 0 relative to the second diet transition (STEP2). Plasma concentrations of SAA were greater on d 1, 3, and 7 compared to d 0 during STEP1 (P = 0.01), while during STEP2 and STEP3, SAA concentrations increased (P < 0.01) from d 0 to 3. During STEP2, PAP steers tended to have lower (P = 0.08) RT than CON steers. Neutrophil and monocyte counts were the least during STEP3 (P < 0.01), whereas expression of CD11b and CD62L was the least through forage feeding (P < 0.01). Concentration of starch in the diet was correlated to all the variables tested (P ≤ 0.01), except for the percentage of B cells (P = 0.22). Yet only ruminal pH, RT, monocyte, and neutrophil counts presented strong correlation coefficients. In conclusion, the step-up transition from forage to high-grain diets triggered systemic inflammation in beef steers as observed by increased plasma concentrations of haptoglobin, serum amyloid A, and expression on adhesion molecules in leukocytes. However, feeding polyclonal antibody preparations against Streptococcus bovis, Fusobacterium necrophorum, and lipopolysaccharide did not provide benefits to mitigate inflammation.

Yeast fermentation product improves pre-transit antioxidant defense and post-transit performance of beef steers

Steers supplemented Diamond V NaturSafe, a yeast fermentation product, at the manufacturer’s current recommended dose for receiving cattle (12 g/steer/d) during a 19-d preconditioning period exhibited greater antioxidant (glutathione) capacity prior to a 19-h transit event. Regardless of treatment, activity of the antioxidant enzyme Mn-superoxide dismutase was increased post-transit, suggesting more antioxidants may be needed to combat transit-induced stress. Supplementing NaturSafe at 12 g/steer/d during both preconditioning and receiving also improved feedlot performance early in the receiving period (d 0 to 30). These data suggest increasing antioxidant status may be an effective strategy to help cattle prepare for and recover from a stressful event, such as long-distance transit.

309 Nutrient Digestibility of Beef Steers Consuming Finishing Diets with an Added Nutritional Packet

The effects of a nutritional packet fed to beef steers during the final 64 d of the feedlot finishing phase on apparent total tract nutrient digestibility were evaluated. Angus-crossbred steers (n =120; initial BW = 544 ± 52 kg) were assigned to 30 pens (4 steers/pen; 15 pens/treatment; pen = experimental unit) in a randomized complete block design. A steam-flaked corn-based finishing diet was fed ad libitum and treatments applied as follows: 1) control and 2) 30 g/steer-daily (DM-basis) of the nutritional packet [containing live yeast (Saccharomyces cerevisiae; 8.7 Log CFU/g), vitamin C (5.4 g/kg), vitamin B1 (13.33 g/kg), NaCl (80 g/kg) and KCl (80 g/kg)]. The nutritional packet used ground corn as a carrier and was included at 1% of diet DM. Orts were quantified daily (if any) and subtracted from the total dietary DM offered to calculate DM intake. Fecal samples were collected twice daily (0700 and 1700 h) for 5 consecutive days (d 47 to 51) from at least 3 steers within pen. Feed samples were collected daily at time of feeding (0630 h). Fecal and feed samples were composited to represent the collection period, dried (55oC), ground (1 mm), and analyzed to assess DM, OM, NDF, ADF, and hemicellulose. In situ (288 h) iNDF was used as an internal marker to measure apparent total tract nutrient digestibility. Data were analyzed using the GLIMMIX procedure of SAS. Intake of DM, OM, and fiber components during the digestibility period was not affected (P ≥ 0.44) by treatment. Steers fed the nutritional packet had increased apparent total tract digestibility of OM (P = 0.02), DM (P = 0.01), NDF (P = 0.02), ADF (P = 0.01), and hemicellulose (P = 0.08; tendency). Improved nutrient digestibility without affecting nutrient intake may warrant an enhanced energy deposition in the carcass.

178 Grazing Toxic Endophyte-infected Tall Fescue Alters Monocyte Abundance and White Blood Cell Expression of Prolactin and NF-kB Pathway Genes in Beef Steers

The hypotheses tested were that (a) summer-long (84 d) grazing of endophyte-infected tall fescue (TE) would alter the count of circulating leukocytes (WBC) and WBC expression of key prolactin and NF-kB pathway genes and (b) that ad libitum intake of an 1:1 blend (MIX) sodium selenite (ISe) and SELPLEX vs ISe in a vitamin-mineral mix (V-M, 27 ppm Se) would ameliorate negative TE effects. Sixteen TE-naïve beef steers depleted of Se were randomly assigned to ad libitum consumption of ISe vs MIX for 35 d. Within Se-form treatments, 2 steers (ISe = 316±37 kg, MIX = 314±39 kg) were randomly assigned to graze each of 4, 2-acre TE paddocks for 84 d and had ad libitum access to their respective V-M. Paddock was the experimental unit (n = 4). The MIXED procedure of SAS was used to assess effect of grazing TE (d 0 vs 84), Se-form (ISe vs MIX), and their interaction on clinical parameters WBC, and relative mRNA content (RT-PCR) in blood. Whole blood Se was 24% greater (P < 0.01) for MIX steers and decreased (P < 0.01) 34% by d 84. Serum prolactin decreased 88% by d 84 and was 98% greater (P < 0.01) for MIX steers on d 84. Monocytes decreased (P < 0.01) 47% with TE and were 67% lower (P = 0.04) in MIX steers. Grazing of TE altered mRNA content of CISH, STA5B, PPIB, AGAP2, and SPRLR; and IL-8, RELA, NFKBIA, TLR, IKBKG, ZAP70, and LCK; of the prolactin (P ≤ 0.05) and NF-kB (P ≤ 0.04) pathways, respectively. In contrast, Se form had no effect (P ≥ 0.07) on mRNA content. Summer-long consumption of TE by steers altered monocyte numbers and expression of prolactin and NF-kB genes, but ad libitum intake of MIX Se forms did not ameliorate these effects.